lvs（dr）与keepalived（主备高可用）（5）
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                echo 1 > /proc/sys/net/ipv4/conf/all/arp_ignore 
                echo 1 > /proc/sys/net/ipv4/conf/lo/arp_ignore 
                echo 2 > /proc/sys/net/ipv4/conf/all/arp_announce 
                echo 2 > /proc/sys/net/ipv4/conf/lo/arp_announce

                ifconfig lo:0 172.18.21.69 broadcast 172.18.21.69 netmask 255.255.255.255 up
                route add -host 172.18.21.69 dev lo:0

